Switching methods and structure with multi-output tubes



SlN-PIH FAN ET AL SWITCHING METHODS AND STRUCTURE WITH MULTI-OUTPUT TUBES Filed Sept. 7, 1957 3K TARGETS CATHODE 3 Sheets-Sheet l INVENTORS SIN-PIH FAN RUDOLPH A. COLA J LWMWMM ATTORNEY y 1958 SIN-PIH FAN AL SWITCHING METHODS AND STRUCTURE WITH MULTI-OUTPUT TUBES Filed Sept. 7, 1957 5 Sheets-Sheet 5 FIG. 7a

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FIG. 5

FIG. 7

PIH FAN RUDOLPH A. COLA INVENTORS SIN- ATTORNEY FIG. 6

, nited States inc SWITCHING IVIETHODS AND STRUCTURE WITH MULTI-OUTPUT TUBES Sin-Pih Fan and Rudolph A. Cola, Philadelphia, Pa., as-

signors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Application September 7, 1954, Serial N 0. 454,288

18 Claims. (Cl. 315-21) This invention relates to beamv switching tubes and circuits and more specifically it relates to systems for stepping an electron beam from one stable position to another in response to successive incoming trigger pulses.

In copending Sin-Pih Fan application for Beam Switching Tubes, filed September 7, 1954,, Serial No. 454,287, issued September 17, 1957. as Patent: 2,806,979, a reliable method of switching beam tubes from successive incoming trigger pulses is disclosed together with tube, structure for carrying out the switchin process. However, the tube structure described in that application is more complex than desirable for mass production techniques and is not well adapted for universal Operation.

Accordingly, it is an object of the present invention to provide simplified beam switchingtube structure for reliable switching operation from single and successive input trigger pulses.

It is a general object of the invention to provide improved beam switching tubes and systems.

It is another object of the invention to provide beam switching tubes capable of switching in response to input trigger pulses of any polarity and. any magnitude or wave shape exceeding the minimum requirements.

Improved tube structure provided y the invention therefore is responsive to single or successive. input trigger pulses to step the beam from one stable position to the next. Electrodes are arranged to permit the trigger pulse to advance the beam from a stable. static. lockedin position to a second or semi-stable. dynamic locked-in position lastingfor the duration of the. input trigger pulse. As the trigger pulse. ends, the beam is in an unstable position and therefore proceeds to the next adjacent stable static locked-in position.

The tube electrode structure comprises an auxiliary holding electrode for keeping the beam, in. the. Semi-stable position, together with field forming structure, such as an additional electrode, for directing the beam away from the auxiliary holding electrode so that it impinges substantially entirely upon an output target. electrode in the static locked-in beam position. occurring in the absence of a switching trigger pulse. from an external Source.

A more detailed discussion of the structural features of the invention and the operational principles thereof follows with reference to the accompanying drawing, in which:

Fig. 1 schematically shows a system constructed in accordance with the principles of the invention for stepping an electron beam from one stable position to another in a multi-compartment tube in response to successive trigger pul Figs. 2a to 2e are plan views of portions of the tube shown in Fig. 1 indicating the manner of operation of the tube in practicing the invention;

Fig. 3 is a partial sectional view of a beam tube constructed to operate in accordance with the invention;

Figs. 4a to 4c are graphs illustrating operational characteristics employed in the invention;

Figs. 5 and 6 are plan views of further tube sections embodying the invention; and

Figs. 7a to 7c are fragmentary schematic diagrams of circuits for coupling beam tubes in direct cascade circuit in accordance with the invention.

Throughout the drawing, like reference characters are used to designate similar features in order to facilitate comparison of the several embodiments of the, invention.

In Fig. l a multi-position beam switching tube is shown schematically together with associated circuit components for operating the tube. The tube itself comprises an elongated. cathode. 10 about. which other electrodes are concentrically arranged to define a plurality of compartments for receiving the beam. in each of these compartments is a. beam. receiving target. electrode 12. Each of these targets is coupled individually to a potential source E of about 70 volts by a, corresponding one of the. 3.000 ohm target. resistors R which are. schematically shown in order to simplify the drawing.

The target, electrodes are each positioned to receive the beam as it passes between two adjacent spade electrodes 14 and 16. These spade electrodes serve to direct the beam to the target, electrodes by means of both the electric field and a magnetic field B having flux lines parallel with the cathode 10 and extending from the plane of the drawing. By Well known principles, the beam will flow between two adjacent spades when one is at a low potential in the order of the cathode potential, and the other is at a higher potential. For this reason, each of the spade electrodes is supplied with an individual resistor R coupling the respective spades to the 100. volt supply terminal E to reduce the potential of one spade of a compartment and cause the beam to become locked in position as beam current. flows. through the corresponding spade resistor.

In order to initially set the beam to impinge upon a 0 compartment, the normally closed zero set switch 18 is provided. This switch 18. in conjunction with resistor 29 connected serially from the O spade resistor to ground serves to isolate the O Spade and reduce its potential with respect to the remaining spades so that a beam will be formed. between the 0 and l spades to thereby be directed to the "0 target.

A further norma y closed clear ng h. 24 is provided for extinguishing the beam by removing the spade potential E simultaneously from all of the spades. As this switch 24 is opened, all the spades are connected to ground potential by the parallel resistors 20 and 22. This effective removal of the electric field causes the electrons to rotate in a tight curve in a counterclockwise direction and return to cathode because of the magnetic field B. The beam does not reform after restoration of the field until the zero set switch is opened or one spade is otherwise. reduced in potential to form the necessary cam path between two spade electrodes.

In the tube structure of Fig. 1, three extra electrodes are supplied in each compartment in addition to the targets and the spades. They are labeled grids 1, 2, and 3, Fig. 21; reading from the spade 16 counterclockwise. More specifically, these electrodes are respectively a switching electrode 30, an auxiliary spade electrode 2.8, and a field forming electrode 26. Each field forming electrode is connected by the common lead 32 to a minus four volt source at terminal 34. The auxiliary spade electrodes .are likewise coupled by a common lead 35 through a potential dropping resistor 36 to the volts spade supply potential terminal 38. An input pulse terminal 40 is connected commonly with each switching electrodeby way of lead 42. Input pulses at this terminal are caused to change the direct current level from four volts to thirty volts. One salient feature of this invention is that reliable switching may be performed with successive input pulses 44 or other changes in direct current level applied directly to the commonly connected switching electrodes.

In order to understand the effect of the three extra electrodes on the electron beam, refer to the views of Fig. 2. Thus, Fig. 2a depicts the beam in a static condition in the absence of an input trigger pulse. The characteristics of the respective tube condition is graphically displayed in Fig. 4a. The graph of Fig. 4a shows that the circuit parameters shown in Fig. 2a result in a characteristic such that the beam current I to the auxiliary holding electrode has bistable properties with the two stable conditions 50 and 52 designated by intersections of the load line 54 and the auxiliary spade current I In the stable static condition 52 the beam is formed as in Fig. 2a, with enough going to trailing spade 14 to hold the spade substantially at zero potential and lock the beam into position. The remainder of the beam is directed almost solely to the target electrode 12 by action of the field forming electrode 26, and as shown on the graph of Fig. 4a the leading spade (j-l-l) draws little current I (j-l-l).

As shown in Fig. 2b the beam configuration begins to change when a positive switching pulse arrives upon the switching electrode 30, and the characteristics change to those of Fig. 4b, where there is only one stable state 61. This results in an eventual beam configuration like that of Fig. 20, where the auxiliary spade 28 receives beam current and locks the beam into this configuration, which is termed a semistable beam position since it remains until the switching pulse expires (or until the switching grid level is returned to its original more negative potential of about four volts). I

When the switching pulse expires, the condition of Fig. 2d occurs. Although this corresponds to the stable position 50 of Fig. 4a, it is termed an unstable beam position because of the large amount of current I '+1) to the leading spade. This, because of the spade resistor, reduces the potential so that the beam is locked into a stable position corresponding to that of Fig. 2a in the next compartment. The potential relationship of electrodes of Figs. 2a through 2d are graphically shown in Fig. 2e for comparison purposes.

Thus, a positive input pulse is supplied only to the switching electrode to afford switching of the beam from one compartment to the next. For illustration, consider specifically the conditions existing as indicated by the waveforms of Fig. 4c and the respective graph of Figs. 4a and 4b. Consider the first two successive positive input pulses 60 and 62 to the switching grid 1. The target j is initially at low potential 63 because of beam impingement in the compartment 1', which causes current to flow through the target resistor. This corresponds to the conditions of Fig. 4a which results in the beam remaining in a single stable position 52. However, at a change in direct current level caused by the leading edge of trigger pulse 60, the conditions of Fig. 4b prevail and the stable position 61 occurs. However, a portion of the beam is diverted to the auxiliary holding electrode 28 as shown in Fig. 20, thereby accounting for the step 64 in target potential, and serving to lock the-beam into a semi-stable position until expiration of the trigger pulse 60. It has been found that the width and amplitude of the trigger pulse is not critical after it exceeds the minimum requirements, and therefore the switching operation is highly reliable without intermediary shaping circuits.

The next change occurs at the trailing edge of the input trigger Waveform returning to its original potential of 4 volts. Thus, the beam goes into the unstable condition of Fig. 2d where the switching electrode becomes more negative, and causes the beam to proceed to the (j+ l) compartment because of current (Ij-l-l) to the leading spade 16. This same operation continues from compartment to compartment in response to single in- 4 put trigger pulses until the beam again cycles into compartment. j when the subsequent input trigger pulse 65 causes a similar switching action from compartment 1' to compartment (j+l).

It is therefore evident that the beam is switched from one of its multiple output positions to another by a series of actions causing the beam to go from its stable position into a semi-stable holding position for the duration of the input trigger pulse and then into an unstable switching position from which it proceeds to the next stable position. The only active elements necessary for such an operation are the auxiliary holding electrode and the switching electrode. Therefore, a magnetron beam switching tube may be constructed as shown in. Figs. 3 and 5 with the holding electrodes 28 and 2S, and switching electrodes 30. In these tubes the beam forming feature is accomplished without an additional electrode by forming the edge 70 of the spade electrodes. 14' to produce the desired electric field configuration.

The auxiliary holding electrode 28' of Fig. 5 is made in the form of a plate to present more surface to the beam. This serves the dual function of shielding the: beam from effects ofthe electric field about the target and of collecting bearncurrent over a larger range of beam position to thereby further increase the switching stability.

In Fig. 3, two target electrodes 12' and 13 are provided for each compartment so that separate output signals may be derived in the stable and semi-stable beam positions.

As shown in Fig. 6,-the tube may be modified to have a plurality of semi-stable positions in each compartment. In this manner a single tube may be used to count up to N times I, when N is the number of semi-stable positions and J is the number of compartments. For example, this could be a decade counter for counting up to 100, and has the advantage of separate output targets so that they may be connected for indicating the count at each of the 100 counting steps if desired. Conversely as many of the targets 100, 101, etc., as desired may be coupled together and connected for commutating or timing action with a single output circuit, or simply connected to a potential source for supplying the necessary field for the stepping operation.

As in the hereinbefore described embodiments, all the switching electrodes 30' may be connected to a single input lead for reliable counting in response to successive trigger pulses. Thus, if desired they may take the form of a sheet within the tube rather than the separate electrodes shown. The auxiliary holding electrodes of each Nth level 280, 281, etc., also may all be connected together. However, separate load resistors, as schematically indicated in part by the diagram of Fig. 6, are required for each Nth level to provide separate semi-stable beam positions.

When beam tubes produce output signals of the type described and are switched reliably from one stable out: put condition to the next by successive input trigger pulses, or other corresponding changes in direct current level, they may be cascaded for decade counting purposes, or the like, in any of the methods suggested by Figs. 7a through 70. Thus, in Fig. 7a the output potential at any one target 12 may be coupled by the lead directly to the switching electrodes of a subsequent tube. The only criterion that is necessary is the provision of proper operating potential gradients which may readily be supplied by those skilled in the art where, direct current coupling is used. However, alternating current coupling is entirely adequate and because of the potential gradient problem is usually preferred.

In Fig. 7b, the output coupling is taken from one auxiliary holding electrode 28. Thus, the decade counting action takes place as the beam is being switched into a semi-stable position rather than a stable position. As evident from Fig. 7c, the same action may be derived from auxiliary target 12' and lead 80", or conversely the switching, action may be completedduring thetenureof the beam in its stable condition by. derivation of the-trig.- ger, pulse target, 12' and lead 80'.

It is evident from the foregoing detailed description: of thestructure and operation of the invention thatimproved apparatus and methods are provided resulting in more reliable switching with tubes. Accordingly, those novel features believed descriptive of the nature and. scope of the invention are defined with particularity in the appended claims.

What is claimed is:

1. A switching system comprising in, combination, a multiple compartment beam tube having an. elongated cathode, a plurality of spade holding electrodes surrounding the cathode, a plurality of beam receiving target electrodes positioned exterior to the spade electrodes to receive the beam when it passes between two adjacent spade electrodes, at least one auxiliary holding electrode, and corresponding switching electrode adjacent; to. one spade electrode in each tube compartment, means forming a magnetic field with flux lines parallel to the elongated cathode, a circuit coupled to saidtube providing. operating potentials for forming a beam which follows an equipotential path established between adjacent electrodes, a circuit coupled to each spade electrode. for h lding the beam in a stable locked-in position responsive to beam current flow to the individual spadeelectrode, a circuit for coupling an input switching pulse commonly-to all the switching electrodes, and circuit means for causing the beam to step from a stable locked-in, position on one spade electrode to at least one semi-stable locked-in: position on the adjacent auxiliary holding electrode: for the duration of an input trigger pulse coupled to the switching electrode, whereby upon cessation of the trigger pulse the presence of magnetic field and the change of electric field together cause the beam to progress to the next adjacent holding electrode to become locked into a corresponding position.

2. A system as defined in claim 1 wherein the tube has a further field forming electrode positioned between the spade electrode and an associated target electrode and shaped to direct substantially the entire beam upon the target in its stable position in conjunction with an external potential source connected thereto.

3. A system as defined in claim 1 wherein the tube has for each of its compartments both a main target electrode for receiving the beam in its stable locked-in position and an auxiliary target electrode positioned to receive the beam when in its semi-stable locked-in position.

4. A system as defined in claim 1 wherein a plurality of auxiliary holding electrodes together with corresponding switching and target electrodes are positioned in the tube between two adjacent spade electrodes to provide a plurality of semi-stable beam positions between two adjacent stable beam positions.

5. A system as defined in claim 1 wherein a plurality of tubes are provided for cascade coupled operation, and each tube has a coupling circuit between an electrode and the commonly connected switching electrodes of the succeeding tube.

6. A system as defined in claim 5 wherein the electrode is one of the target electrodes.

7. A system as defined in claim 5 wherein the electrode is one of the auxiliary holding electrodes.

8. A magnetron beam switching tube of the type employing crossed electric and magnetic fields including an elongated cathode oriented substantially parallel to the lines of flux of said field, a plurality of beam forming and holding spade electrodes concentrically positioned about said cathode, a plurality of target electrodes positioned to receive beam current passing between two adjacent spade electrodes, a field forming electrode positioned between each spade and target electrode to direct substantially the entire beam to the target electrode, an auxiliary holding electrode positioned adjacent each field forming 6 electrode, and a, switching lectrode positioned adjacent each auxiliary holding electrode.

9 A magnetron beam switching tube of the type employing crossed electric and magnetic fields having an elongated cathode oriented substantially parallel to the lines of flux of said field, at least two beam forming and holding spade electrodes positioned in said field away from. said cathode at least one target electrode positioned to receive the beam as it is passed between the two spade electrodes in response to normal static operating conditions, and an auxiliary holding electrode positioned between said spade electrodes to lock the beam into an altered dynamic operating position between the spade electrode and a switching electrode between said spade electrodes to move the beam from its normal to its altered position.

10. A magnetron beam switching tube having means for aligning an external magnetic field, an elongated cathode oriented substantially parallel to the, lines of flux of said field, at least two beam forming. and holding spade electrodes positionedin said field away from said cathode, at least one target electrode. positioned to receive the beam as it is passed between thetwo spade electrodes in response to normal static operating conditions, and an auxiliary holding electrode positioned between said spade electrodes to lock the beam into an altered dynamic operating position between the spade electrode, and switching means to move the beam, from its normal to its altered position, said switching means comprising another electrode positioned between said spade electrodes.

11. In a beam switching tube, a plurality of holding electrodes, a plurality of auxiliary holding electrodes for at least one of the holding electrodes, a plurality of target electrodes for receiving the beam in various positions adjacent the holding and auxiliary holding electrodes, and a plurality of switching electrodes adjacent to said auxiliary holding electrodes for advancing the beam from one of said holding electrodes to the next through intermediate positions at the auxiliary holding electrodes.

12. A system for operating a beam switching tube including a plurality of holding electrodes, a plurality of auxiliary holding electrodes for at least one of the holding electrodes, a plurality of target electrodes for receiving the beam in various positions adjacent the holding and auxiliary holding electrodes, said system comprising a separate switching electrode for each of said holding electrodes and said auxiliary holding electrodes for advancing the beam from one of said holding electrodes to the next through intermediate positions at the auxiliary holding electrodes, a source of successive input trigger pulses, and a circuit commonly coupling all of theswitching electrodes for simultaneous energization in response to the trigger pulses.

13. The method of operating a magnetron type multicompartment beam switching tube having beam forming and holding, auxiliary beam holding and beam switching electrodes for each compartment comprising the steps of, applying potentials to the tube electrodes to cause the beam to impinge upon a selected compartment, applying a positive switching pulse to the beam switching electrode and thus changing the position of the beam in said selected compartment,. and terminating said positive switching pulse and thereby switching the beam to an adjacent compartment.

14. The method of operating a magnetron type multicompartment beam switching tube having beam forming and holding, auxiliary beam holding and beam switching electrodes for each compartment, comprising the steps of, applying potentials to the tube electrodes to cause the beam to impinge upon the beam holding electrode in a selected compartment, said potentials including a static beam switching electrode potential, applying a change in direct current potential level to the switching electrode to cause the beam to impinge upon the auxiliary beam holding electrode in said selected compartment, and restoring the beam switching electrode to its static po- 7 tential to thereby cause the beam to switch to an adjacent compartment.

15. A magnetron beam switching tube adapted to be operated with crossed electric and magnetic fields having an elongated cathode for providing an electron beam, a plurality of electron beam forming and holding spade electrodes concentrically positioned about said cathode, a plurality of target electrodes positioned to receive electron beam current passing between two adjacent spade electrodes, each target electrode being associated with a spade electrode, an auxiliary holding electrode positioned between each spade electrode and its associated target electrode, and a switching electrode positioned adjacent to each auxiliary holding electrode for switching an electron beam from one operating position to another.

16. A magnetron beam switching tube having an elongated cathode for providing an electron beam, a plurality of generally U-shaped electron beam forming and holding spade electrodes concentrically positioned about said cathode, a plurality of target electrodes positioned to receive electron beam current passing between two adjacent spade electrodes, each target electrode being associated with a spade electrode and having an arm positioned between the sides of its associated spade electrode, an auxiliary holding electrode positioned between each spade electrode'and its associated target electrode and positioned adjacent to said arm of the target electrode, and a switching electrode positioned adjacent to each auxiliary holding electrode.

17. An electron tube for operation under the influence of crossed magnetic and electric fields comprising an elongated substantially evacuated envelope, a thermionic cathode centrally disposed therein and adapted to be positioned parallel to said magnetic field, an array of similar spades disposed adjacent to said cathode, each of said spades having a trough-shaped transverse cross section, the sides of saidspades extending generally awayfrom said cathode, an array of similar target electrodes disposed adjacent to said array of spades and on the open side thereof which is more remote from said cathode and laterally displaced with respect to said spades, each of said target electrodes having a beam receiving surface and one side angularly disposed therewith, the side member of each of said target electrodes extending inwardly into the trough of a spade with which it is associated and positioned closer to one side of the spade, a flange extending from the other side of each of said spades toward said one side, a generally L-shaped electrode positioned between said flange of each spade and the beam receiving surface of its associated target electrode, and a beam switching electrode positioned adjacent to said L-shaped electrode.

18. The tube defined in claim 17 wherein each of said L-shaped electrodes includes one arm oriented perpendicular to the beam receiving surface of the associated targetelectrode and another arm oriented substantially parallel to said flange on the associated spade electrode,

' References Cited in the file of this patent- UNITED STATES PATENTS 

